Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Chloride Incorporation Process in CH3NH3PbI3-xClx Perovskites via Nanoscale Bandgap Maps



Jungseok Chae, Qingfeng Dong, Jinsong Huang, Andrea Centrone


CH3NH3PbI3-xClx perovskites enable fabrication of highly efficient solar cells. Chloride ions benefit the morphology, carrier diffusion length and stability of perovskite films; however, whether those benefits stem from the presence of Cl- in the precursor solution or from their incorporation in annealed films is debated. In this work, the photothermal induced resonance (PTIR), an in situ technique with nanoscale resolution, is leveraged to measure the bandgap of CH3NH3PbI3 xClx films obtained by a multicycle coating process that produces high efficiency (≈ 16 %) solar cells. Because chloride ions modify the perovskite lattice, thereby widening the bandgap, measuring the bandgap locally yields the local chloride content. After a mild annealing (60 min, 60°C) the films consist of Cl-rich (x < 0.3) and Cl-poor phases that, upon further annealing (110 °C), evolve into a homogenous Cl-poorer (x < 0.06) phase, suggesting that methylammonium-chrloride is progressively expelled from the film. Despite the small chloride content, CH3NH3PbI3 xClx films show better thermal stability up to 140 °C with respect CH3NH3PbI3 films fabricated with the same methodology.
Nano Letters


mixed-halide perovskites, PTIR, bandgap, nanoscale mapping, solar cells


Chae, J. , Dong, Q. , Huang, J. and Centrone, A. (2015), Chloride Incorporation Process in CH3NH3PbI3-xClx Perovskites via Nanoscale Bandgap Maps, Nano Letters, [online],, (Accessed June 19, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created December 8, 2015, Updated October 12, 2021